Modification of cellulosic articles



Allg- 29, 1961 R. c. sovlsH ET AL 2,998,329

MODIFICATION OF CELLULOSIC ARTICLES Filed Aug. 5, 1957 IN VEN TORS/ffc/)oro/ C. 5 o 1//5/1 Fra/7k L. Sounders TZ'ORNEYS United Stal-'e5Patent 2,998,329 t MDDIFICATION F CELLUL'OSIC ARTICLES Richard C. Sovishand Frank L. Saunders, Midland,

Mich., assignors to'The Dow Chemical Company, Midland, Mich., acorporation of Delaware Filed Aug. S, 1957, Ser. No. 676,057 14* Claims.(Cl. 117-93) Many articles that consist Ior are comprised of essentiallyor substantially pure cellulosic materials have certain physicalproperties and ycharacteristics that, advantageously and quitedesirably, might Well be improved upon. Included in such class, inparticular, may be cotton and other natural cellulosic textile fibersand various artificial shaped articles of cellulose that has beenreconstituted or regenerated, for example, by either the viscose,cuprammonium or analogous processes. Typical of reconstituted cellulosearticles are the viscose 'rayon types of so-called artificial silktextile fibers and regenerated cellulose films for wrapping andprotective purposes, among other uses.

By Way of delineating certain of the referred-to deficiencies, it isWell known, for example, that unmodified cotton fiber has a tendency torot. Viscose rayon, as either a filamentous or filmiform shaped article,may be similarly afflicted. In addition, viscose rayon has notorioussusceptibility to being adversely affected by water. Thus, such forms ofregenerated cellulose may generally be characterized by theirv ratherpoor Wet strength and reduced resilience in the presence of moisture.

The attempts to overcome these and cognate difiiculties in textilematerials of cotton and viscose rayon and in regenerated cellulose filmhave literally been legion. The dissatisfactorily low rot resistance ofcotton, for example, has been the basis for many ameliorative treatingand processing techniques thereupon, including cyanoethylation of thenatural fiber or cloth and fabric textile materials constructedtherefrom. Likewise, many polymeric `and resinous coatings and finisheshave been proposed and employed both for cotton, viscose rayon and thelike substantially pure cellulosic textile fibers and the articles intowhich they are converted in order to augment and improve theirresistance to rotting, moisture, wrinkling and for multitudinouscorollary and analogous purposes. Regenerated cellulose films havereceived a great deal of attention that is akin to that which iscursorily alluded t0 in the foregoing.

The chief aim and concern of the present invention is to provide animproved and signicantly superior method for modifying shaped articlesof various substantially pure cellulosic articles and materials,particularly cotton and viscose rayon fibers and cloth and fabriccomprised thereof and constructed therefrom and film structures ofregenerated cellulose, by providing them With at least a superficialcoating or 'chemically modified surface, or both, or even a likepenetrating subsurface effect, of certain monomeric substances that areadapted to chemically polymerize to form a polymeric or resinous coatingfor or over the cellulosic substrate or to react chemically with thecellulosic substrate or to graft copolymerize with the cellulosicsubstrate to form' a chemically bound polymeric or resinous superficiallayer thereover or permeated section thereof, or to beneficially modifythe substrate by combination effects of the indicated varieties. It isalso a purpose and design of the invention to furnish the advantageouslyenhanced products of the above delineated method.

According to the present invention, a substantially pure cellulosicsubstrate in shaped article form (including cotton and viscose orcuprammonium rayon fibers and cloth and fabric constructed therefrom andregenerated cellulose lm) may advantageously be modified for improvementin and benefit to one or more of its basic physical Patented Aug. 29,1961 ICC properties and characteristics such as rot resistance andwater-proofness or hygroscopicity by a method which comprises firstcontacting, and, if desired, impregnating, the cellulosic substrate Withan aqueous solution `of a Water-soluble monomer that is polymerizable inaqueous solution under the inliuence of a field of ionizing high energyradiation; then subequently exposing the cellulosic substrate in contactwith the aqueous monomeric solution (and, advantageously, at leastpartially swollen thereby) to a field of ionizing high energy radiationuntil at least the surface of the substrate has become modified With-reacted monomeric material. As has been indicated, the reactedmonomeric material may become chemically attached to the cellulosicsubstrate, as is the case when cotton and other cellulosic bers aremodified with acrylonitrile by practice of the present invention, or itmay graft copolymerize thereon and thereto or may merely form anintimately bonded and firmly attached physical polymeric or resinouslayer or coating or impregnated section, or both, on or in the substrateas a result of polymerization of `the water soluble monomer. In anyevent, and without being restricted to particular mechanisms by whichthe desired improvement may be achieved and effected, the properties ofthe cellulosic substrate are ameliorated and enhanced in one or moreways, depending on the particular monomeric material or mixture ofmonomers that is employed and the specific effects that they are capableof achieving and the properties and characteristics they are adapted tocontribute in and for the substantially pure cellulosic substrate.

Thus, when aqueous solutions of acrylonitrile are employed Ion and withcotton fibers or cloth (and like cellulosic substrates) an extremelyefficient and remarkable degree of improvement is readily andexceptionally uniformly achieved in the substrate. Products havingexcellent rot resistance may accordingly be excellently and easilyprovided. Likewise, other monomers can be made to modify the cellulosicsubstrate by polymerization or graft copolymerization with thecellulose, or both, Within or on (or with and on) the cellulosicsubstrate to form tightly adhering, polymeric or resinous layers orimpregnated sections, or both, that are capable of mildew orwater-proofing the substrate; benefitting its Wrinkle resistance;improving or altering its dye-receptivity characteristics; etc.,depending on the functional characteristics and inherent behaviorism ofthe chemical product of the reacted monomer. All this may generally beaccomplished, incidentally, Without disturbing or appreciably alteringthe visual appearance or hand of the substrate being modified.

As has been indicated, the monomer that is employed for modifying thecellulosic substrate must be water-soluble and capableof beingpolymerized in aqueous solution under the influence of a field ofionizing high energy radiation. And, as mentioned, the method of theinvention must be performed with the monomer in aqueous solution Whilein contact with the cellulosic substrate being modified. In thisconnection, as is contemplated herein, the water-soluble monomers thatare suitable for use in the practice of the present invention includethose that are only soluble in Water to a limited degree and which maysometimes be considered for other purposes as not being completelyWater-miscible despite the fact that they actually dissolve in Water tothe slight extent that is adequate for their utilization according tothe instant invention. Surprisingly enough, the presence of water duringthe radiation is a criticality that cannot be avoided if the optimumbenefit and advantage of the present invention is to be achieved. Asremarkable and inexplicable as it may seem, decidedly inferior or noresults are obtained when the cellulosic substrate is irradiated when itis in contact with only the monomer alone. Vlvl'oclification withacrylonitrile bears excellent evidence of this. The firmly attached andbonded pick up of cotton fiber or cloth irradiated inthe presence ofacrylonitrile alone is generally either an immeasurable or negligiblequantity (say up to 2 percent by weight, at best). Or, at the otherextreme the article, such as cloth, that is being modified may actuallybecome embedded in such an enveloping, solid mass of extrinsicpolyacrylonitrile as to literally be rendered useless for any practicalpurpose. To the contrary, cotton that has been irradiated in thepresence of an aqueous solution of acrylonitrile readily picks up fiveto ten times as much of the chemically attached reaction product as inthe best results of irradiation of the same monomer without utilizationof the aqueous medium. Furthermore, most conventional, non-aqueoussolvents such as dioxane, methyl ethyl ketone, benzene, absolute ethanoland the like do not provide the same outstanding and apparently uniqueadvantage as water. Such solvents, when employed to dissolve the monomerfor purposes of furnishing a contacting monomeric solution to use withthe cellulosic substrate, do not, in general, alter the dissatisfactoryor less beneficial results that are achieved when only the pure monomeris directly employed to contact the substrate being irradiated.

Practice of the present invention provides 'and secures many `benefitsand advantages. The improvement and simplification in modifyingcellulosic articles with acrylonitrile is evident in the foregoing. Inan analogous way, the substrate may be provided with a desired polymericor resinous coating by merely irradiating a cloth, fabric or otherdesired article while it is in contact with an aqueous solution ofsuitable monomer, then washing and drying the irradiated and modifiedarticle. In general, no chemical catalyst is needed. Practice of thepresent invention, of course, obviates the tedious conventionaltechnique for applying resinous coatings which ordinarily involvesdissolving or dispersing the polymer that is desired for providing theintended coating in a suitable solvent, coating the resultingcomposition on the cloth, removing excess solvent, etc. A cellulosicfabric that has been beneficially modified in accordance with thepresent invention is schematically depicted in the sole gure of thehereto annexed drawing.

Advantageously, the Water-soluble monomer that is employed for modifyingthe cellulosic substrate in the practice of the present invention isselected from the group consisting of acrylonitrile, methacrylonitrile,acrylamide, acrylic acid, methyl methacrylate, sulfonated styrenemonomers (including the free acid and salt forms thereof), particularlythose sulfonated in the para position, vinyl lactam monomers(particularly N-vinyl'lactam monomers such as those disclosed in U.S.Patent No. 2,265,450 and especially N-vinyl pyrrolidone) and methylisopropenyl ketone. The concentration of the aqueous solution of themonomer that is employed may vary over relatively wide ranges.Ordinarily, within the limits of water solubility, it is beneficial toemploy a monomeric solution that contains from l or 2 to 10 or 15percent by Weight (based on the weight of the solution) of the dissolvedmonomer although, in certain cases, particularly with vinyl lactammonomers, much more concentrated aqueous solutions, say up to 50 or morepercent, may be employed suitably. Enough of the monomeric solutionshould be applied to or made available in intimate contact with thecellulosic substrate to permit the desired take-up or pick-up of reactedmonomer product to be achieved in or on the substrate. When aqueousacrylonitrile solutions are being employed for the modification, use ofa monomeric solution that contains about 5 percent by weight ofdissolved monomer generally brings optimum results. Little, if any,additional pick-up of reaction product by the cellulosic substrate seemsto be brought about by utilization of more concentrated aqueousacrylonitrile mixtures including those having as much as 25 percent byweight of incorporatedmonomer. The

.4 5 percent acrylonitrile solutions have good dissolution of themonomer and seem to result in minimized derivation of straighthomopolymer product. If desired with acrylonitrile or other monomers,mixtures of water and lower alkyl alcohols such as methanol and the likeor other water miscible solvents may be suitably employed in thepractice of the invention to secure greater concentrations of dissolvedmonomer.

Generally, a satisfactory result may be `achieved when a minorproportion of reacted product is impregnated in or provided on thecellulosic substrate, or both. In some instances, very minor proportionsmay suffice, especially when low levels or degrees of modification aredeemed satisfactory for a particular purpose at hand. It is difficult togeneralize on the weight proportions that may be utilized in allinstances due, as may be readily appreciated, to the relatively widedivergence in the specific characteristics of the various cellulosesubstrates that may be improved by practice of the present invention andthe variations in the monomers and their reaction products that may beused. Broadly speaking, it may be desirable to impregnate or contact thesubstrate with such a quantity of the aqueous monomeric solution as willprovide between about 1 and 40 percent by Weight of the monomer for theirradiation induced reaction in the presence of the substrate. For mostpurposes an amount of solution that will provide from about 5 to 20percent of monomer in contact with the substrate may be quite suitable.

It is most desirable and of greatest economical value for all orsubstantially al1 of the monomer that is employed to be reacted to aproduct under the influence of irradiation that is picked-up by thecellulosic substrate through either chemical interaction or attachmentor physical adherence of a polymer product, or both. Thus, it isbeneficial in most instances for the radiation to be continued until allor substantially all of the monomer that has been placed in contact inaqueous solution with the substrate is picked up as a reacted product bythe substrate. The irradiation, incidentally, may be performed While thesubstrate is actually immersed in the aqueous monomeric solution or,frequently with greater advantage, with the solution being merelyapplied to the substrate as by spraying or spreading the solution on thesubstrate or dipping the substrate into the solution and wringing it toa desired monomeric content prior to irradiation. Maximum benefit andsuperior effects of modification, particularly as regards pick-uppotential, are frequently obtained when substantially neutral (oressentially neither acidic or basic) impregnating solutions areemployed. Thus, lower pick-ups are invariably encountered withacrylonitrile on cotton when the monomer is dissolved in 1 percent byweight aqueous solutions of either sodium hydroxide or hydrochloricacid. This phenomenon is hereinafter more particularly demonstrated.

The high energy radiation which is employed for inducing themodification of the cellulosic substrate with the reaction product ofthe aqueous monomeric solution that is in contact therewith is of theionizing type which provides emitted photons having an intrinsic energyof a magnitude which is greater than the planetary electron bindingenergies which occur in the reacting monomeric materials and thecellulosic substrates in the modifying reactions (such as straightchemical interaction, graft copolymerization and the like) in which theybecome involved. Such high energy radiation is conveniently availablefrom various radioactive substances which provide beta or gammaradiation as, for example, radioactive cobalt, nuclear reaction fissionproducts and the like. If it is preferred, however, high energyradiation from such sources as electron beam generators, X-raygenerators and the like may also be utilized. It is beneficial to employthe high energy radiation in a field of at least about 40,000roentgensper hour (or equivalent ionizing potency) intensity, A roentgen, as iscommonly understood,

epesses is the amount of high energy radiation as may be provided in aradiation field which produces in one cubic centimeter of air at 0 C.and 760 millimeters of absoous solution of the monomer and thesubstantially pure cellulosic substrate are under a mutal inflence inthe field of high energy radiation. Room temperatures and atmosphericpressures may be employed satisfactorily for the e *Y irradiation,although, in certain instances, it may be desired to accomplish themodification of the substrate at elevated temperatures and even undersuperatmospheric pressures. The preferred radiation dosage in millionroentgen equivalent physicals (mrep.) that is employed is an amount orquantity that is adapted to quickly accomplish the desired modificationwithout deleteriously influencing or degrading the reacted monomerproduct or the cellulosic substrate, or both. Usually, dosages betweenabout 0.1 and 5.0 mrep. at rates of from 0.04 -to 1.0 mrep. per hour aresuitable for the achievement of such end. Obviously, the greatesteconomy and advantage may be achieved when the minimum high energyradiation dosages are involved. Excessive dosages should be avoided,especially after all or substantially all of the irradiation-inducedmodifying reaction has occurred.

The invention is further illustrated in and by the following examples,wherein unless otherwise indicated, all parts and percentages are to betaken by weight.

EXAMPLE 1 Three pieces of square woven cotton fabric having individualdimensions of about 11/2 by 8 inches that were obtained from about 2.5ounces to the yard stock and which weighed 0.701; 0.724; and 0.672grams, respectively were each immersed in an aqueous solution of about4.2 grams of acrylonitn'le in 55.8 grams of Water. The solution,containing the cloth samples immersed therein, was then purged withnitrogen and subjected to a field lof high energy ionizing irraditionfrom a cobalt-60 properties as the sample of cotton fabric that wasirradiated in air.

Substantially equivalent results were obtained when the foregoing wasrepeated excepting to eliminate the purge with nitrogen or to replace itbypurging with air. Similar results were also obtained when theforegoing was repeated excepting to effect a total dosage of about 1.0

Y Y mrep. for the modification.

` on the substrate during the time that the applicating aque fl lookedexactly like the original, although it had a very Y slightly differenthand (or feel to the touch), being slightly less sleazy in this respect.The modified fabric dyed more easily with Calcomine R, a direct dye,than did the unmodified material. Its rot resistance was much betterthan that of the unmodified cotton and at least as good in this respect,for example, as conventionally cyanoethylated materials. It couldwithstand a load of about 37.2 pounds at breaking (according to thestrip tensile test of A.S.T.M. D-39-49) and had an elongation of about4.9 percent. The unmodified cotton fabric had aV breaking load of 34.2pounds and 5.4 percent elongation. The same fabric, after having beensubjected to the same irradiation While immersed in plain water Withoutbeing in contact with any modifying monomer, had a breaking load of 39.6pounds and an elongation of 6.4 percent. Plain cotton fabric that wassubjected alone to `a 5.0mrep, dosage was found to have a breaking loadof 30.7 pounds.

In contrast with the foregoing, when the same fabric was immersed inpure monomeric acrylonitrile and sub- A jected to the same irradiatinginfluence while so immersed, i. it was found to have experienced only a1.6 percent permanent pick up and to have essentially the same physicalCommensurate results were yalso yachieved when the foregoing wasrepeated excepting to replace the cotton fabric being modified withheavier 10 ounce cotton duck fabric.

EXAMPLE 2 EXAMPLE 3 The procedure of the first example was repeated withaqueous solutions of 3.5 percent acrylamide, 5 percent methylisopropenyl ketone, 3.5 percent acrylic acid, 5 percent Isodium styrenep-sulfonate and 5 percent N-vinyl py-rrolidone. The pick ups that Wereobtained on the cotton fabric substrate of each of the reaction productsof the monomer after the 0.5 mrep. irradiation dosage were 7.2 percent,30.9 percent, 4.0 percent, 7.9 percent and 0.9 percent, respectively.The samples that were modified with the reaction products of thesulfonated styrene monomer land the Vinyl lactam monomer could be dyedstrongly with both basic and acid dyestuffs such as those that were usedin the second example. The dye-receptivity of the so-modified fabric wasmuch more pronounced than that of the unmodified cotton.

In contrast with the above no pick-up could be achieved when theirradiation was performed on cotton fabric immersed in solutions ofiacrylonitrile in dioxane, methyl ethyl ketone, benzene or ethanol orsolutions of styrene in methanol or methyl ethyl ketone.

EXAMPLE 4 The procedure of Example 3 was repeated with the same 2.5ounces to the y-arn cotton fabric excepting to use an aqueousimpregnating solution which consisted of about 6 parts of acrylonitrilemonomer land 1 part of vinylpyrrolidone monomer dissolved in Water toprovide 'a total dissolved monomer concentration of about 7 percent.About 8.4 percent pick-up was achieved in the fabric modified with thereaction products of the monomer mixture. The modified fabric hadexcellent properties and characteristics and was not easily visuallydistinguishable EXAMPLE 5 Tlhe general procedure of the foregoingexampleswa's repeated with several monomers in separate aqueoussolutions including acrylonitrile (VCN), sodium styrene sulfonate(NaSS), methylrnethacrylateV (MM) Vand methyl isopropenyl ketone (MIK).In each case (excepting for the control` sample) a high energy radiationdosage of about 0.5 mrep. was effected. The control sample (A4?) was notsubjected yto irradiation. fThe results that" were obtained Iare `setforth and included in the following Table I, which indicates the amountYof pick-up that was obtained in each case as well las certain of thephysical properties of each of the samples tested. The table `alsoincludes data relative to each impregnating solution that was utilizedand in certain instances, indicates dose rates that were `applied at alower level of radiation than the standard 0.5 mrepJlJLthat was used forall of the samples where not otherwise indicated. Y

Table I RADIATION OF COTTON FABRIC WITH VARIOUS MONOMERS Weight PercentBreaking Sample Monomer Solvent and Monomer Concentration Pick-up,Elonga- Strength,

Percent tion lbs.

Irrad. in Air 6.1 41. 7 Irrad. in Na 5. 9 41. 0 Irrad. in H2O 6. 4 39. 6Control- 5. 4 n 34. 2 Water, 7 percent, Nitrogen purge 5. 9 4. 9 35. 2Water, 7 percent, No Nitrogen purge-. 9.0 5. 7 42.0 A7 5 1 percent NaOH,7 percent 2. 7 A8 5 1 percent HC1, 7 percent 2. 5 A9 Water, 7 percent,0.0466 mrcp./hr. 7.4 4. 7 30.3 "A10" 5 Water, 7 percent, 0.093 mrepJhr.9. 3 5.1 36.0 A11, 5 Water, 7 percent, 0.466 InrepJh 10. 2 4.9 37. 2 A12Water, 5 percent 1. 6 4. 7 30. 1 A13 Water, 1% percent..- 3. 7 4. 5 30.4"A14" Water, 5 percent 80.9 4. 5 33. 0

Irradiation of the cotton fabric alone indicates that slight degradationoccurs between 1 and 5 mrep. At 5 mrep., slight yellowing of the fabricoccurs, and there is a slight drop in breaking load.

EXAM PLE 6 In order to specifically illustrate the improvement in rotresistance `that may be obtained with cotton fabric when it `has beenmodified according to the present invention, la sample of 2.5 ounces tothe yard cotton fabric prepared as in Example 1 yand modified withacrylonitrile so as to have an 11.6 percent pick-up was buried in richgarden loam under outdoor conditions for a period of xabout three weeks.For purposes of comparison, a sample of untreated cotton fabric wasburied along with the modified material as well y.as a third sample ofcotton that Was unmodiued excepting to subject it to `a dosage of 0.5mrep. Both the untreated control `and the unmodified irradiated cottonsamples were disintegrated at the end of the indicated period of burial.The former was found to have become completely disintegrated. Onlyfragments remained of the latter sample. The modified cotton sample,however, remained in excellent condition after the three week period.This clearly demonstrated its remarkable rot and stain resistance.

EXAMPLE 7 The general procedure of Example 4 was repeated with a 5.2ounces to the yard viscous rayon fabric using aqueous monomericimpregnating solutions for modification. Each of the samples tested(excepting for the unirradiated control sample Bl) was subject to atotal dosage of about 0.5 mrad. (0.93 mrep. equalling one mrad). Theresults lare set forth in the following Table 2, wherein the wetstrength at break of each fabric sample is indicated this technique. Thecaustic pretreated modified fabric product was neither uniformly coatednor free from em bedded homopolymer. In addition, the fabric sample wasfound to have become discolored. The experiment indicated that causticpretreatment of the fabric does not improve the results that may beobtained in the practice of the present invention.

EXAMPLE 9 The general procedure of Example 1 was repeated, excepting toattempt to secure the modification of the fabric by the monomer throughthe influence and action of conventional peroxide type catalystinitiators instead of by means of irradiation. Thus, potassiumpersulfate, hydrogen peroxide-ferrie chloride; and benzoyl peroxide inwater methanol mixtures were employed as separate catalyzing systems inattempts to modify the fabric with acrylonitrile monomer. `In each case,the cotton fabric gained considerable weight. However, in each instance,the coating that was obtained consisted largely of easily extractablehornopolymer that was embedded in the fabric and which was neitheruniform nor free from physical blotchiness. The results obtained by theimmediately foregoing technique which is not in accordance with theinvention were quite in contrast to those obtained when the modificationof the fabric is achieved under the inuence of high energy radiation. Inthe latter case, as is lapparent in the foregoing specification anddescription, the fabric Aretains the appearance of the unmodified cottonmaterial. Furthermore, very uniform dyeing of the modified fabric may beachieved when along with its elongation. the fabric has been modified inaccordance with the pres- Table II MODIFICATION OF VISCOSE RAYON FABRICWITH VARIOUS MONOMERS Solvent Monomer Weight Wet Percent Sample MonornerConcentration Pickup, Strength,b Elonga- Remarks percent lbs. tion B1None.. 33.8 16.4 Control. "B2". None. 34.5 19.5 Irrad. Control. B3.VON--. Sample d'scarded; cloth completely embedded in large mass ofhomopolymer "B4. VCN.-- Water, 7percent.. 5.8 36.6 19.3 Uniform. "B5.VCN Water,7percent 9.0 38.1 18.7 Wetting Agent Tergrtol P-28 used withimpregnating solution. "B6 MM Wate', 1% per- 5.1 33.7 17.6

cen B7 NaSS..- Water, 2% per- 10.6 31.3 19.9

cent.

I Impossible to calculate.

b 0.05 percent Triton X-100n wetting agent used in aqueous solutionemployed for wetting in test.

EXAMPLE 8 Cotton fabric was pretreated with a 2 percent aqueous sodiumhydroxide solution before irradiating it according to the procedure ofExample 1 in the presence of a 7 percent water solution of acrylonitrilemonomer. Dissatisfactory and poor results were obtained following entinvention. Substrates containing substantial quantities of embeddedhomopolymer, however (such as those which were derived with the aboveindicated catalyst systems) are not capable of being level dyed and,when they are dyed, result in obviously contrasting shades of colorationas a result of the undesirable heterogeneity of their compositions.

Several samples of modified cottontabric prepared as in the foregoingExample 1 in accordance with the present invention were extracted `withvarious solvents by allowing the modified cotton sample to stand in alarge excess of solvent for one week `at room temperature to determinethe loss in weight experienced as a resnlt of the extraction. One of thesamples, modified with acrylonitrile to a 9 percent total pick-up, lost2.5 percent of its total weight in dimethyl tormamide (DMF). Thiscorresponded to a loss of 28 percent of the pick-up weight. Anothercotton sample, modified with 10.2 percent of acrylonit-rile, lost 2.1percent of its weight in the extraction test with DMF; corresponding toa loss of 21 percent of pick-up Weight. A cotton fabric sample, modifiedWit-h 30.9 percent pick-up of methyl isopropenyl ketone, lost 2 percentof its total weight when extracted in the indicated manner with methylethyl ketone. This corresponded to a loss of 6 to 7 percent in pick-upweight. A sample of l ounce cotton duck, modified with acrylonitrile toa 20.4 percent pick-up, lost 3.2 percent of its toal weight on standingin DMF for one hour. This loss corresponded to a loss of about 16percent in pickup weight.

EXAMPLE ll Several samples of cotton fabric weighing about 2 grams eachthat were about 1V: inches wide and 8 inches long were separately placedat the bottom of several glass trays, each containing aqueous percentsolutions `of acrylonitrile monomer. While so immersed, the samples weresubjected to high energy irradiation using a 2 million electron volt Vande Graaff generator that was being operated with a beam current of 162microamperes. Each of the samples was permitted to remain in the beam ofhigh energy electrons for a different period of time in order to effectdifferent dosages In addition, sample C4 whichr had the 10.8 per centpick-up was subjected to extraction with DMF yfor 5 days at atempera-ture of 40 C. No appreciable weight loss was observed in thesample as a result of the extraction treatment. In comparison, thepolyacrylonitrile homopolymer that formed in the aqueous phase duringthe irradiationwas, as'might be expected, quite soluble in the DMFsolvent. The same sample, after its modification, was exposed for a220hour period to ultraviolet light in an Atlas Fadeometer. Nodiscoloration of the modified fabric was noted asl a result of this eX-posure.

EXAMPLE 12 Several samples of regenerated cellulose film (conventionalcellophane) were modified by a procedure similar to that set forth inExample 5 using several different monomers for the modificationincluding VCN, NaSS, vinyl methyl ketone (VMK) and methyl acrylate (MA).In two of the samples that were attempted to be modied with VCN, bothaqueous ethanol and dioxane solvent media were tested. These weresamples D4 and D5, respectively. Each of the samples was irradiated fromcobalt-60 source at a rate of 0.2 mrep. per hour until a total dosage ofabout 0.5 mrep. had been effected. The results are set forth in thefollowing Table IV which includes a description of the monomer solutionemployed (excepting for the control sample D1 which was irradiated whilebeing immersed in plain water) as well as weight pick-up values thatwere observed, both as corrected to take into account the considerablel'oss in weight in each of the films that was experienced during thesoaking in water and washing of the modified samples, based on theresults obtained with the control sample, and where such correction wasnot taken into account to indicate the total gain in weight, if any, ofthe modified film (despite weight losses due to washing).

Table IV MODIFIED CELLOPHANE FILMS Weight Pick-up Sample MonomerConcentration of Impregnating Remarks Medium Not Corrected D1 NoneIrradiated inplain water Weight loss equivalent to about 19 percentpick-up. D2 VCN lopercent aqueous solution. 3.7 18.6 D3 VGN... Immersedmpure monomer Emledded solidly with homoo er. D4 VON.-. ltpercentaqueous ethanol solu- 8.3 p ym lon. D5 VCN... 10 percent dioxanesolution 3.8 D6 NaSS--. 10 percent aqiueous solution 8.3 Dyed readilywith basic dye. D7 VME .flo 5.6 15.2 Sample washed thoroughly withacetone, cloudy. D8 MA -do 31.1 42.5 Do.

for accomplishment of the fabric modification. lIn the All of themodified films became slightly cloudy during following tabulation thereare set forth the results obtained with several of the samples that wereexposed for different periods of time and which each had receiveddifferent high energy dosages.

Table Ill MODIFICATION 0F COTTON FABRIC USING VAN DE GRAAFF GENERATOR ASSOURCE 0F HIGH ENERGY IRRADIATION Time 1n Dosage in Weight Pick-up 6 5Sample Beam, mrads. of Modified Seconds Fabric, percent 5. 6 0.25 1. 0211.2 0.50 3.2 22. 4 l. 00 G. 8 44. s 2.00 1o. 8 7 0 the treatment andtended to assume a brittle condition, probably through loss ofplasticizer which was not replaced after the treatment to effect thedesired modifcation had been completed.

What is claimed is:

1. Method for beneficially modifying substantially pure cellulosicsubstrates which comprises first contacting the substrate with anaqueous solution, in a substantially neutral pH, of a water-solubleethylenically unsaturated monomer that is polymerizable in aqueoussolution under the influence of a field of ionizing high energyradiation; continuing contact of said substrate with said monomericsolution until the former is at least partially swollen by the latter;then .subsequently expos ing the cellulosic substrate while it is incontact with the aqueous monomeric solution to a field of ionizing highenergy radiation until at least the surface of the substrate has becomemodified with the saturated reaction product of said monomeric materialthat has been chemically reacted to provide said reaction product in the11 presence of and in intimate association with said substrate.

2. The method of claim 1, wherein the substrate is comprised of cottonbers.

3. The method of claim 1, wherein the substrate is comprised ofregenerated cellulose.

4. The `method of claim 1, wherein the substrate is comprised of viscoserayon bers.

5. The method of claim 1, wherein the tield of ionizing high energyirradiation that is employed for the modi- 'fying reaction has anintensity of at least about 40,000 roentgens per hour.

6. The method of claim 1, wherein the amount of water-soluble monomer inaqueous solution that is in `contact with said substrate is an amount ofthe monomer between about 1 and 40 percent by weight, based on the,weight of the substrate. 7. The method of claim 1, wherein the amountof water-soluble monomer in aqueous solution that is in contact withsaid substrate is an amount of the monomer between about 5 and 20percent by weight, based on the weight of the substrate.

8. The method of claim 1, wherein said substrate being contacted by saidaqueous monomeric solution is irradiated at a rate of from 0.04 to 1.0mrep. per hour `until a dosage of from 0.1 to 5 mrep. is effected.

9. The method of claim 1, wherein said monomer is 'selected from thegroup consisting of aerylonitrile, meth- 12 acrylonitrile, acrylamide,acrylic acid, methyl methacrylate, sulfonated styrene monomers, vinyllactam monomers and methyl isopropenyl ketone,

10. The method of claim 1, wherein said monomer is a para-sulfonatedstyrene monomer.

11. The method of claim 1, wherein said monomer is vinyl pyrrolidone.

12. The method of claim 1, wherein said monomer is acrylonitrile.

13. Modifying a cotton ber substrate with acrylonitrile by a methodaccording to the method set forth in claim 1.

14. As an article of manufacture, an article Ythat is comprised of amodified substantially pure cellulosic substrate that has been preparedby a method which is in accordance with the method set forth in claim 1.

References Cited in the le of this patent UNITED STATES PATENTS2,863,812 Graham Dec. 9, 1958 2,883,361 Handy et al. Apr. 21, 1959FOREIGN PATENTS 1,079,401 France May 19, 1954 66,034 France Apr. 24,1956 (Addition to 1,079,401)

750,923 Great Britain June 20, 1956 Notice of Adverse Decision inInterference iIn Interference No. 93,422 involving Patent No. 2,998,329,R. C. Sovish and F. L. Saunders, MODIFICATION yOF CELLULOSIC ARTICLES,

` final judgment adverse to the patentees was rendered Apr. 21, 1964, esto claims 1, 2, 3, 4, 5,117, 9, 10,11, 12, 13 and 14. [Oycz'al GazetteMay 18, 1965.]

1. METHOD FOR BENEFICIALLY MODIFYING SUBSTANTIALLY PURE CELLULOSICSUBSTRATES WHICH COMPRISES FIRST CONTACTING THE SUBSTRATE WITH ANAQUEOUS SOLUTION, IN A SUBSTANTIALLY NEUTRAL PH, OF A WATER-SOLUBLEETHYLENICALLY UNSATURATED MONOMER THAT IS POLYMERIZABLE IN AQUEOUSSOLUTION UNDER THE INFLUENCE OF A FIELD OF IONIZING HIGH ENERGYRADIATION; CONTINUING CONTACT OF SAID SUBSTRATE WITH SAID MONOMERICSOLUTION UNTIL THE FORMER IS AT LEAST PARTIALLY SWOLLEN BY THE LATTER;THEN SUBSEQUENTLY EXPOSING THE CELLULOSIC SUBSTRATE WHILE IT IS INCONTACT WITH THE AQUEOUS MONOMERIC SOLUTION TO A FIELD OF IONIZING HIGHENERGY RADIATION UNTIL AT LEAST THE SURFACE OF THE SUBSTRATE HAS BECOMEMODIFIED WITH THE SATURATED REACTION PRODUCT OF SAID MONOMERIC MATERIALTHAT HAS BEEN CHEMICALLY REACTED TO PROVIDE SAID REACTION PRODUCT IN THEPRESENCE OF AND IN INTIMATE ASSOCIATION WITH SAID SUBSTRATE.